recently my etwow scooter has been acting up. i've finally pin point it to a cable that has been cut due to stress.
all photos are here and you can see the cut wirehttps://imgur.com/a/C2Giv

should i just solder the cut wire in yellow? would the solder be strong enough?
or should i just get the cable replacement from ebay? what is it called?
one end of the cable is female with 9 pin, but only 8 wire is actually used. the yellow, green, and blue are really thick. because the yellow is cut, the scooter can sometimes slow down or jerk around.
pls help, thanks!

If you cut away the plastic around the broken wire and can get a good solder joint, it should work OK. Tape it up well so the joint doesn't move. It's also helpful to see if there was an issue with the wire routing that caused it to break in the first place.

Looking at the bike bits in the background, it appears the connector is floating in a point of high motion. Ideally you want the cable on both sides of the connector tied to a frame component where they're not moving at all.

The issue arose because of the absence of an adequate strain relief at the transition from the inflexible connector body to the flexible cable. This led to stress at the point of discontinuity - right where the cable meets the body.

If you are stuck with a floating mount like this, sleeve the body and cable with two or three layers of increasingly long heat shrink. Start with a short piece (5/8-3/4") then layer on slightly longer pieces so the cable/sleeve becomes increasingly flexible as you move away from the connector. This will distribute the stress harmlessly over a longer length of cable (maybe 2"). This is the identical gimmick that you see on wall warts, power tool cords, etc where the cord leaves the device.

If you do fechter's fix above and sleeve the result like this, it should last longer than you'll own the bike...

connectorHighStressPoint.png (85.25 KiB) Viewed 809 times

Sleeve with heatshrink so flexibility changes more slowly

heatShrinkStrainRelief.png (1.57 KiB) Viewed 809 times

If you don't have shrink on hand, a less tidy but fair second best is self-fusing silicone tape or self-fusing rubber tape available at your local Home Depot or Harbor Freight ('Stretch and Seal' or 'Self Bonding Super Tape') - just be sure to get a 'tapered thickness' application.

teklektik is correct about the lack of strain relief. If you use marine heatshrink it has hot glue inside so you dont need as many layers... although the best way I have found is to put some hotglue in there for strain relief, let it cool enough, then put heatshrink on, and heat the whole thing with a heatgun so that the hotglue softens and heatshrink tightens it all together, making a clean, neat strain relief.

Warning:This post is being read via light, a substance known to the state of California to cause cancer.